For the same reason Wikipedia has a ton of disambiguation pages for dealing with multiple concepts that have the same name: so you know which particular thing you're talking about, instead of just going "oh I heard that word once" and going off on a lengthy tear about what turns out to be a totally different thing with the same name.
Wikipedia is a general purpose store of knowledge. Comments exist in a context. In this case, discussion of geomancy.
More precisely I would say that the context is "discussion of a site about geomancy-the-divination-method", not "discussion of geomancy-the-landscape-related-magic-system" or "discussion of anything called geomancy".
It’s like conflating palm reading with astrology.
Irrespective of whether you believe the methods have any value, we should at least make sure we’re talking about the same thing.